2025-12-29 – Weekly Geology News : Rock that floats: exploring pumice

Last week, our forum discussions were rich with practical insights and debates. Members focused on the nuances of geochemical data in resource modeling and shared experiences with the challenges of soil anomalies in gold exploration. There was also a lively exchange about the efficacy of continuing education courses for professional development hours, and some technical discussions about using portable NMR devices in tight sands.


This Week’s Hot Topics

Leveling up geochem for resource models
A deep dive into how geochemical data can enhance resource models sparked discussion on best practices and innovative approaches.
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Rock that floats, no tricks
This thread explored the fascinating phenomenon of rocks that float, with a focus on pumice and its geological significance.
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Which PDH courses actually pay off
Professionals debated which continuing education courses truly add value to a geologist’s career, providing practical advice on selection.
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Portable NMR on tight sands — useful or noise
A technical discussion questioned the reliability of portable NMR devices in assessing tight sands, weighing benefits against potential drawbacks.
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PESTPP-IES tips for sustainable yield targets
Experts shared insights on using PESTPP-IES to set realistic and sustainable yield targets, with a focus on groundwater management.
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Soil anomalies, disappointing gold grades
Explorers exchanged stories of unexpected soil anomalies affecting gold grades, offering lessons learned and mitigation strategies.
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Geochem QA/QC and cutoff tools
This thread dissected the role of QA/QC in geochemical analysis and discussed tools that help in determining accurate cutoff grades.
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Carlsbad twinning on a roadside feldspar
A curious observation of Carlsbad twinning in feldspar prompted a conversation about its formation and identification in the field.
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From outcrop to Outlook calendar
Geologists shared tips on managing field data and integrating it into digital tools for better project management.
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Phase II scope creep with PFAS
Discussions revolved around the challenges of managing scope creep in Phase II environmental site assessments, especially with PFAS concerns.
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Thanks for staying engaged with our community. Looking forward to another week of insightful discussions and shared knowledge. Take care!

1 Like

On ‘soil anomalies’ for gold, use MAD-based thresholds; check regolith mapping first.

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Quick example: on a greenfields program in WA, our gold-in-soil signal only showed up after we ran a short “orientation line” across a known shear and switched to B-horizon clay (<180 µm) with aqua regia; surface lag was masking it… If the regolith’s patchy, sanity-check with As/Sb ratios before chasing highs so you don’t over-interpret noise.

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In pumice-rich terrain, our soil geochem went noisy until we pre-soaked samples and skimmed floatables before riffle splitting — ‘pumice is the popcorn of rocks’, @geo_jules. That simple tweak tightened Au-in-soil anomalies without changing thresholds. Minor caveat: it’s only worth the fuss where floatables are obvious or >1–2% by mass.

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Piggybacking on @bryan_lee92’s sampling note, in aircore across pumiceous tuffs we cut noisy Au by pre-wetting the cyclone, switching to antistatic PVC bags, and going by mass not volume — “weigh, don’t scoop.” Pumice acts like packing foam and rides the airflow, so if humidity’s low a quick mist over the splitter helps; otherwise log bag mass so lab dilutions don’t chase fluff.

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We improved Au/Cu repeatability in pumicey cover by running an ionizing bar over the riffle splitter and clipping a ground lead to the cyclone — the static was making chips fly like confetti. Cheap kit borrowed from the electronics bench, but double-check your mass balance because it can nudge split ratios, @geo_jules.

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